Urushiol-induced contact dermatitis (also called Toxicodendron dermatitis and Rhus dermatitis ) is the medical name given for allergic rashes produced by oil urushiol, which contained in a variety of plants, mainly from the genus Toxicodendron : Chinese varnish trees, poison ivy, poison oak, and poison sumac. The name is derived from the Japanese word for the sap of the Chinese varnish tree, urushi . Other crops in the Sumac family (including mango, pistachio, Burmese varnish, Indian marker tree, and cashew shell) also contain urushiol, as well as unrelated plants such as Ginkgo biloba.
As with all contact dermatitis, an urushiol-induced rash is a type IV hypersensitivity reaction, also known as delayed type hypersensitivity. Symptoms include itching, inflammation, fluid, and, in severe cases, a burning sensation.
The American Dermatology Academy estimates that there are up to 50 million cases of urusiol-induced dermatitis each year in the United States alone, accounting for 10% of all time lost injuries in the US Forest Service. Poison oak is a significant problem in rural West and South America, while most poison ivy is rampant in the Eastern United States. Dermatitis from toxin sumac is less common.
Video Urushiol-induced contact dermatitis
Signs and symptoms
Urushiol causes eczematous contact dermatitis characterized by redness, swelling, papules, vesicles, abrasions, and scratches. People vary greatly in their sensitivity to urushiol. In about 15% to 30% of people, urushiol does not trigger an immune system response, while at least 25% of people have a very strong immune response that results in severe symptoms. Since skin reactions are allergic, people may develop stronger reactions after repeated exposures, or have no immune response to their first exposure but show sensitivity to subsequent exposure.
About 80% to 90% of adults will get a rash if they are exposed to 50 micrograms of purified urushiol. Some people are so sensitive that it takes only urushiol (two micrograms, or less than one ten million ounces) of skin to start an allergic reaction.
This rash takes one to two weeks to walk and can cause scarring, depending on the severity of the exposure. Severe cases involve small blisters (1-2 mm), obviously, filled with fluid on the skin. Vesicles containing liquids containing whitish fluid may indicate infection. Most of the ivy rashes, without infection, will disappear within 14 days without treatment. Excessive overloading may cause infection, generally by staphylococcal and streptococcal species; this may require antibiotics.
Maps Urushiol-induced contact dermatitis
Cause
Contact dermatitis caused by urushiol is caused by contact with plants or other objects containing urushiol oil. The oil is attached to almost anything touching, like towels, blankets, clothes, and landscaping tools. Clothing or other materials that touch the plant and then, before washing, touching the skin is a common cause of exposure.
For people who have not been exposed or have not been allergic to urushiol, it may take 10 to 21 days for a reaction to occur for the first time. After allergy to urushiol, however, most people come out 48 to 72 hours after contact with oil. Typically, individuals have been exposed at least once, if not several times, before they develop a rash. The rash usually lasts one to two weeks, but in some cases it can last up to five weeks.
Urushiol is primarily found in the space between the cells under the skin outside the plant, so the effect is less severe if the plant tissue remains undamaged when in contact. After the oil and resin are washed out of the skin, the rash is not contagious. Urushiol does not always spread after binding to the skin, and can not be transferred once urushiol has been cleansed.
Although simple skin exposure is the most common, urushiol consumption can lead to serious systemic reactions. Burning plant matter is usually said to create smoke containing urushiol that causes systemic reactions, as well as a rash in the throat and eyes. Firefighters often get rashes and inflamed eyes from smoke-related contacts. High temperature campfires can burn urushiol before it can cause damage, while a burning fire can evaporate volatile oil and spread it as white smoke. However, some sources deny the dangers of burning plant material containing urushiol.
Mechanism
Urushiol is oxidized in-vivo, producing a quinone form of the molecule. Its toxic effects are indirect, mediated by an induced immune response. Oxidized urushiol acts as haptens, chemically reacting with, binding, and converting integral membrane proteins to exposed skin cells. Affected proteins interfere with the ability of the immune system to recognize these cells as normal parts of the body, causing T cell-mediated immune responses. This response is directed to the urine-derivative derivative complex (ie, pentadecacatechol) bound to skin proteins, invading cells as if they were foreign matter.
Treatment
Treatment consists of two phases: stopping urushiol contact that causes a reaction (this should be done in a few minutes) and, later, reducing the pain and/or itching.
Primary treatments include washing the affected skin thoroughly with soap, water, and friction as soon as possible after exposure is discovered. Soap or detergent is needed because urushiol is oil; friction, with a duster or something similar, is necessary because urushiol is firmly attached to the skin. Commercial preparation preparations, which are available in areas where vines grow, usually contain surfactants, such as Trionone X-100 nonionic detergents, to dissolve urushiol; some products also contain abrasives.
The US Food and Drug Administration recommends applying a wet compress or soaking the affected areas in cold water; topical corticosteroids (available over-the-counter) or oral corticosteroids (available by prescription); and topical skin protectors, such as zinc acetate, zinc carbonate, zinc oxide, and calamine. Cupcake soda or colloid oatmeal can relieve mild irritation and itching. Aluminum acetate, sometimes known as Burow's solution, can also relieve rashes.
A bath or compress using hot water (but not boiling) may relieve itching for several hours, although it "also taxes the integrity of the skin, opens the pores and generally makes it more vulnerable", and is only useful for secondary treatment (not for skin urine-skin cleansing , which should be done with cold water). Persons who have had previous systemic reactions may be able to prevent subsequent exposure from systemic reversal by avoiding heat and excitation of the circulatory system and applying moderate cold to any skin infected with biting pain.
Antihistamines and hydrocortisone creams, or oral antihistamines in severe cases, can alleviate the symptoms of developing rashes. Unsolicited oral diphenhydramine (US trade name Benadryl) is the most commonly recommended antihistamine. Topical formulations containing diphenhydramine are also available but may further irritate the skin.
In cases of extreme symptoms, steroids such as prednisone or triamcinolone are sometimes given to attenuate the immune response and prevent long-term skin damage, especially if the eye is involved. Prednisone is the most commonly prescribed systemic therapy but can cause serious adrenal stress, so it should be taken with care and slowly lowered. If a secondary bacterial infection of the affected area occurs, antibiotics may also be required.
Rubbing with plain soap and cold water will remove urushiol from the skin if done within minutes after exposure. Many home remedies and commercial products (eg, Tecnu, Zanfel) also claim to prevent urushiol rash after exposure. A study comparing Tecnu ($ 1.25/oz.) With Goop Hand Cleaner or Dial Ultra Dishwashing Soap ($ 0.07/oz.) Found that the difference between the three - in the range of 56-70% improvement without treatment - did not significant ( P & gt; 0,05), but the non-treatment increase was significant at the same level of confidence.
Further observation:
- Normal laundry with detergent will remove urushiol from most clothes but not from leather or suede.
- The liquid from the resulting blister does not spread urushiol to others.
- The blisters should be left undamaged during healing.
- Toxic ivy and poison oak are still dangerous when the leaves have fallen out, because the toxic residue is sedentary, and exposure to plant parts containing urushiol can cause a rash at any time of the year.
- Ice, cold water, cooling lotions, and cold air do not help to cure the poison ivy rash, but cooling can reduce inflammation and calm itching.
- Results for jewelweed as a natural agent for contradictory treatment. Some studies show that it "fails to reduce toxic symptoms of ivy dermatitis" [1980] and "no prophylactic effects" [1997]. Leaf and stem juice Impatiens capensis is a traditional American medicine for skin rashes, including poison ivy and its use has been supported by at least one peer-reviewed study, recently in 2012.
Prevention
A rarely quoted double-blind study in 1982 reported that oral urushiol courses are usually the subject of hyposensitization.
See also
- Poison ivy
- Contact dermatitis
- Anti-itching drugs
- Toxin
- List of skin conditions
References
Source of the article : Wikipedia
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